Cathode-ray device



March 14, 1950 c. H. BABBs CATHODE RAY DEVICE Filed Feb. 25. 1947 Mmm'Inventor Hevber Bcl bbs. @wwwa/3A;

@TUS

Allorney Patented Mar. 14, 1950 y "I Pye Limited, Ca f company "bridge,England, a British Application February 25, 1947, Serial No. 730,719

In Great Britain Marchk 2, 1946 The present invention relates to cathoderay devices, such as cathode ray tubes, monoscopes and electron pickuptubes as used in television, in ywhich the cathode ray beam is focussedand deflected by electromagnetic means, such as by coils disposed aroundtheI neck ofthe tube.

In such devicesthe-deiiecting coils and/or the 'gcathode ray gun mayintroduce astigmatism by distorting the electron beam, and the presentinvention has for its object to provide additional means which introduceastigmatism of the cathode ray beam to compensate for the astigmatismproduced by the deflecting coils and/or the cathode ray gun.

According to the present invention, two magnetic members are disposed atdiametrcally opposite positions with respect to the axis of the cathoderay gun and between the focussing coil and the gun. The magnetic membersare carried by a non-magnetic framework or ring which is adjustable bothrotatably and longitudinally.

In order that the invention may be more clearly understood, referencewill now be made to the accompanying drawings, in which:

Fig. 1 shows a plan View, partly cut away, of a cathode ray tubeincorporating the compensating device according to this invention.

Fig. 2 shows a perspective view of the compensating device.

Referring to the drawings, the neck portion of the cathode ray tube Ihaving the electron gun 2 disposed at its end is surrounded by thefocussing coil 3 and deflecting coils 4 in known manner. According tothe invention two soft iron pins 5 and 6 are supported at diametricallyopposite points of the neck of the tube and between the focussing coil 3and the gun 2 by means of a ring 1 of non-magnetic material. In theembodiment shown the ring 1 is constructed in the form of a tubularmember which is provided with a longitudinal slit 8 to impart slightresiliency to this member and allow it to bear with friction upon theouter surface of the neck portion of the cathode ray tube. At the end ofthe tubular member 'l is provided a collar 8, which preferably has aknurled peripheral edge, by means of which the tubular member and thetwo soft iron pins carried thereby can be adjusted longitudinally alongthe neck of the tube and rotatably therearound. The iron pins 5 and 6are disposed with their axes extending in the direction of the1ongitudinal axis of the tube.

By adjusting the position of the iron pins, both longitudinally androtatably with respect to the focussing coil, astigmatism can beintroduced 6 Claims. (Cl. Z50-157) into the focussing which is such thatit compensates vfor the astigmatism caused by deflecting coilde-focussing and/or by the cathode ray gun. The compensating device isadjusted with the 'scanning voltages applied on the deflecting coils toproduce the sharpest definition of the electron beam;

Whilst a particular embodiment has been described, it will be understoodthat various modications may be made without departing from the scope ofthe invention as defined by the appended claims.

I claim:

1. A cathode ray device comprising an evacuated envelope having a neckportion containing an electron gun, magnetic focussing means andelectro-magnetic deflecting coils surrounding said neck portion, anon-magnetic member adjustable longitudinally with respect to the axisof the gun, two magnetisable members mounted on said non-magnetic memberin diametrically opposed portions with respect to the axis of the gun,said magnetisable members being disposed in the magnetic field of thefocussing means for magnetisas tion thereby.

2. A cathode ray device comprising an evacuated envelope having a neckportion containing an electron gun, magnetic focussing means andelectro-magnetic deflecting coils surrounding said neck portion, anon-magnetic member adjustable both rotatably and longitudinally withrespect to the axis of the gun, two magnetisable members mounted on saidnon-magnetic member in diametrically opposed positions with respect tothe axis of the gun, said magnetisable members being disposed in themagnetic eld of the focussing mea-ns for magnetisation thereby.

3. A cathode ray device comprising an evacuated envelope having a neckportion containing an electron gun, magnetic focussing means andelectro-magnetic deflecting coils surrounding said neck portion, anon-magnetic member adjustable longitudinally with respect to the axisof the gun, two soft iron pins disposed with their axes extending inthe'direction of the axis of the gun mounted on said non-magnetic memberin diametrically opposed positions with respect to the axis of the gun,said soft iron pins being disposed in the magnetic field of thefocussing means for magnetisation thereby.

4. A cathode ray device comprising an evacuated envelope having a neckportion containing an electron gun, magnetic focussing means andelectro-magnetic deflecting coils surrounding said neck portion, a splittubular member of non- 3 magnetic iaterial adjustable at leastlongitudinally with respectI to the axis of the gun, tWo soft iron pinsdisposed with their axes extending in the direction of the axis of thegun mounted on said non-magnetic member in diametrically opposedpositions with respect to the axis of the gun, said magnetisable membersrbeing disposed in the magnetic field of the focussing means vformagnetisation thereby, the intensity of magnetisation being adjustableby longitudinal movement of the non-magnetic member relatively to thefocussing means.

5. A cathode ray device comprising an evacuated envelope having a neck,portion containing an electron gun, magnetic focussing means andelectro-magnetic deecting coils surrounding said neck portion, a splittubular member of non-magnetic material having a collar tofacilitate-manual adjustment of the non-magnetic member .bothrotatablyand longitudinally with respect to the axis of the gun, two soft ironpins disposed with their axes extending in the direction of the `axis ofthe gun mounted on said non-magnetic member .in diametrically opposedpositions with respect to lthe axis of the gun, said magnetisablemembers being disposed in the magnetic field of the focussing means formagnetisation thereby, the intensity of magnetisation being adjustablebylongitudinalmovement of the non-magnetic member relatively to thefocussing means.

6. A cathode ray device comprising an eifachw uated envelope having aneck portion containing an electron gun, an electro-magnetic focussingl.focussing coil to adjust the intensity of mag- 'netsation of the pinsby the magnetic field of the .focussing coil, said carrying member alsobeing .rotatable with the respect to the axis of the gun,

15 L' to adjust the rotational position of 'said pins.

CYRUS H. BABBS..

REFERENCES CITED v'-I"lie'fo1-lowing references are of record in thefile of this patent:

UNITED STATES `PATENTS vNumber

